to start off i have no knowledge on this stuff at all, i have read some of the post on it but still very confused. so i want to add like a 2.5' lift. not a leveling kit or anything just like a body lift.
but i wanna know what all i would have to change if i did do the lift, and which ones are the best for it.
and would that change your gas mileage any?

no you dont have to do anything to your truck. It is not stiffer. I thought it would be but mine wasnt any stiffer.

To add to that, Get the add a leaf kit so you can haul heavier loads.

It will come with spacers for the front. Any auto shop is going to charge you bout $75 to $100 to compress the springs and put the spacers on them and thats if you bring the struts to them off of the truck.